The spinal column is a highly complex system of bones (i.e., vertebral bodies) and connective tissues that provides support for the body and protects the delicate spinal cord and nerves. The spinal column includes a series of vertebrae stacked one atop the other, each vertebral body including an inner or central portion of relatively weak cancellous bone and an outer portion of relatively strong cortical bone. Situated between each vertebral body is an intervertebral disc that cushions and dampens compressive forces on the spinal column. A vertebral canal containing the spinal cord and nerves is located within the forward-facing surface of the vertebral bodies.
There are many types of spinal column disorders. Patients that suffer from such disorders typically experience extreme and debilitating pain, as well as diminished nerve function. Examples of such spinal column disorders include, but are not limited to, scoliosis (i.e., abnormal lateral curvature of the spine), kyphosis (i.e., abnormal forward curvature usually in the thoracic portion of the spine), excess lordosis (i.e., abnormal backward curvature usually in the lumbar portion of the spine), spondylolisthesis (forward displacement of one vertebrae over another usually in the lumbar portion or cervical portion of the spine), etc. There are still other types of spinal column disorders caused by physiological abnormalities, disease and/or trauma such as, for example, ruptured or slipped discs, degenerative disc disease, fractured vertebra, and the like.
Multi-segmental spinal fixation is an accepted surgical procedure in the treatment of such spinal column disorders. It involves the use of a series of pedicle screw assemblies and one or more spine rods. The pedicle screw assemblies each include a screw that is threadedly screwed into one of a plurality of adjacent vertebral bodies. A spine rod (contoured or straight) is fixedly secured to a spine rod clamping body of each one of the pedicle screws for fixing two or more adjacent vertebral bodies in a static relative position. In this manner, spinal fixation can be used to alter the alignment of adjacent vertebrae relative to one another so as to change the overall alignment of the spine, to preclude relative movement between adjacent vertebrae, and the like.
Performing spinal fixation using a minimally invasive surgical procedure is desirable and is becoming more commonplace. A minimally invasive surgical procedure is a surgical procedure that is less invasive than open surgery used for the same type of procedure. Minimally invasive surgery is typically performed through several small incisions (e.g., slits, punctures or the like) as opposed to one or more large incisions as is used in open surgery. By performing the surgical procedure through small incisions, the surgeon can safely work on the site being operated on while disturbing only a minimal portion of surrounding tissue, organs, etc. As a result, patients are less likely to develop complications, they are more likely to recover more quickly, and can typically return to normal activities sooner in comparison to open surgery.
Therefore, pedicle screw assembly that is specifically configured for use in a minimally invasive surgical procedure is advantageous, desirable and useful.